Sky-Watcher Mount connection options

Components

The Tripod and Mount is basically a hardware platform to hold the OTA. The mount has motors to move the OTA around as well as some motor controllers with associated electronics.

The Sky-Watcher hand controller is essentially the brains to control the motors. It is a small computer with a pointing model, an astronomy database, movement controls keys and some routines to assist with various alignment functionality.

All the functions of the hand controller can be replaced and enhanced with applications on a modern personal computer or a mobile phone (the mobile is also a computer with inbuilt GPS that can also make phone calls).

The computer alternative to the hand controller can provide more flexibility on controlling the Mount.

I prefer the modern computer (mobile or laptop) approach with a choice of sophisticated applications rather than the standard Sky-Watcher hand controller option as pictured in Figure 1.

For the visual setup, the Sky-Watcher 'SynScan' application on the mobile with WiFi to the mount (via a WiFi interface if necessary) is a suitable option as pictured in Figure 3.

For the Astrophotographer, basically two options exist as pictured in Figure 2:

If pointing accuracy is important because you need to move to multiple objects over the night, go with ASCOM and the EQMOD or the Windows SynScan applications option. EQMOD is a bit dated, but it has a pointing model with various options on pointing model accuracy as well as an ability to update the pointing model with sync commands from the imaging applications after platesolving.

The second option is for an Astrophotographer that concentrates on one target for the night in order to maximise the signal to noise ratio of the target object. The better option is to use ASCOM and a modern mount controller application such as GSS, as well as an imaging application that does Platesolving to fine-tune initial target location as well as target check after a meridian flip. Accurate tracking/guiding is also an advantage.

The following is based on a Microsoft Windows operating system computer using ASCOM drivers. ASCOM on Windows seems to be the most widely used Astrophotography platform with more available applications.

Options

Figure 1 - SynScan Hand Control driving the mount

Note in reference to Figure 1, the SynScan Hand Controller has a thick black cable supplied to connect to the mount, (TTL) and a thin white cable (RS232) for connection to a computer for software uploads or control as shown. If the computer doesn't have RS232 ports, an RS232 to USB converter (from say JayCar Electronics) is needed as pictured in Figure 1, see USB cable at Serial to Mount connection.

The newer SkyWatcher Mounts have a built-in USB port which so doesn't need a TTL to USB converter cable. A USB cable can be used from the mount to your computer.

'Figure 2 - 'Computer application driving the mount via cable''

Figure 2 shows 3 options of direct serial cable connection to the mount. Only select one of these options. (or use the first WiFi serial interface option in Figure 3 in place of the wired serial options in Figure 2).
Figure 2 also shows 3 options of software to replace SynScan to control the mount (ie. GSS, EQMOD or SynScan application). Only select one of these options.

Using the SynScan in 'PC Direct Mode' (first option in Figure 2) is not recommended as passing commands through the Hand Controller adds a small delay, the Hand Controller is just one more thing to set up and it's one more point of failure.

For information on the USB to Mount cable shown in Figure 1 and Figure 2, see Serial to Mount connection.

Note that only EQMOD and SynScan has a pointing model incorporated. A pointing model is useful if you are doing visual or you don't have client software with Platesolving. If you are doing Astrophotography and use Platesolving to fine-tune your pointing location as well as guiding to track the position, then a pointing model is not important. In this case, GSS being the more modern and full-featured interface is probably the better option.

Figure 3 - Computer & Mobile application driving the mount via WiFi

Re in the above diagram, running Synscan on an iPhone connected to the Mount via WiFi:

Instructions for using SkySafari planetarium with SynScan.
Using SynScan Pro on an iOS device (ie. an Apple iPhone) means you need to run the SkySafari app on a second device such as an iPad if you also need a planetarium. Android mobiles can run both SynScan and SkySafari apps on the same device.
The Luminos planetarium iOS app seems to run on the same iOS device as SynScan app so has the advantage of only needing a single iOS mobile device.

It is also possible to provide a WiFi to Com port adapter to enable the WiFi connectivity option to replace the wired option pictured in Figure 2. See below the options listed below.

Figure 5 - ASCOM Client examples to Sky-Watcher ASCOM Hubs

An ASCOM Hub is an ASCOM driver that handles multiple connections. The ASCOM Hub on mount control applications allows the mount to handle multiple connections which means multiple applications.

Figure 5 shows the 3 ASCOM Hub server application options to control the Sky-Watcher mount with some example ASCOM client applications.

Figure 6 - A typical Client to Mount Example

Figure 6 is an 'end to end' setup example to connect to a Sky-Watcher mount.

A relatively new way of extending ASCOM to other computers (including mobile devices) is via an ASCOM Alpaca client/server interface.

For example, if a client application, such as Cartes du Ciel (CdC) which has an ASCOM Alpaca connection option exists on an IP (Internet Protocol) network that has access to an ASCOM Remote server, then CdC can connect to the Mount's ASCOM hub and control it as if on the same computer. This is pictured in Figure 7.

Figure 7 - An ASCOM Alpaca example

Cabled connections as shown in Figure 6 and Figure 2 are preferred as they are more reliable and quicker to debug issues in the middle of a cold night.

ASCOM Alpaca variations will probably be added with future application development.
For example, an Alpaca interface from say SkySafari on the iPad.

ASCOM

ASCOM's main goal is to provide a driver-client layer to separate astronomy device-specifics from the application software that uses those devices.
See the following ASCOM background information:

EQMOD

Green Swamp Software (GSS)

Sky-Watcher

iOS (iPhone) appilcations mentioned

Other Software mentioned

WiFi connectivity options to replace the wired option.

A wired connection between the Mount and its controller is more reliable than WiFi connection. It is possible to provide 'virtual' Com port access to the WiFi link to allow mount controller applications like GSS and EQMOD to connect to a mount via WiFi.

A free single virtual serial port software which maps to an IP and PORT required by the Wifi adapter.

Virtual Com port access to the SynScan on WiFi

DIY Projects

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